Coiled tubing has been used in many extended reach wells. Due to its inherent characteristics, coiled tubing has rather limited extended reach capability. Many wells that can be successfully drilled by the drillers cannot be properly serviced by conventional coiled tubing deployment techniques. As a result, many technologies have been actively pursued to extend the reach of coiled tubing.
The technologies that have been considered for extending the reach of coiled tubing fall into two different categories: reducing friction or generating pull force downhole. Technologies that aim to reduce friction in order to increase coiled tubing reach include using friction reducing agents and downhole vibration technologies. Technologies for using downhole pull force to increase extended reach are typically based on downhole tractor technology. The downhole tractors available today are either electrically or hydraulically powered. For electrically powered downhole tractors, the pull force generated by available tractors is typically in the order of 1000 lbs. For hydraulically powered downhole tractors, the pull force generated by available downhole tractors is between 4000-8000 lbs. Downhole tractor solutions for coiled tubing deployment tend to be relatively complex and expensive.